This invention relates to novel ester derivatives of prostaglandin A.sub.2 (hereinafter identified as "PGA.sub.2 "), 15-alkyl-PGA.sub.2, 15(R)-15-alkyl-PGA.sub.2, and their racemic forms, and to processes for producing them.
PGA.sub.2 is represented by the formula: ##STR1## A systematic name for PGA.sub.2 is 7-{2.beta.-[(3S)-3-hydroxy-trans-1-octenyl]-5-oxo-1.alpha.-cyclo-3-penteny l}-cis-5-heptenoic acid. PGA.sub.2 is known to be useful for a variety of pharmacological and medical purposes, for example to reduce and control excessive gastric secretion, to increase the flow of blood in the mammalian kidney as in cases of renal dysfunction, to control spasm and facilitate breathing in asthmatic conditions, and as a hypotensive agent to reduce blood pressure in mammals, including humans. See Bergstrom et al., Pharmacol. Rev. 20, 1 (1968) and references cited therein. As to racemic PGA.sub.2, see for example J. Martel et al., Tetrahedron Lett. 1491 (1972).
The 15-alkyl-PGA.sub.2 analog and its 15(R) epimer are represented by the formula: ##STR2## wherein Y' is ##STR3## following the usual convention wherein broken line attachment of hydroxy to the side chain at carbon 15 indicates the natural or "S" configuration and solid line attachment of hydroxy indicates the epi or "R" configuration. See for example Nugteren et al., Nature 212, 38 (1966) and Cahn, J. Chem. Ed. 41, 116 (1964). The 15-alkyl- and 15(R)-15-alkyl-PGA.sub.2 analogs in their optically active and racemic forms are known. See for example Belg. Pat. No. 772,584, Derwent Farmdoc No. 19694T. These analogs are also useful for the above-described pharmacological purposes.
Esters of the above compounds are known, wherein the hydrogen atom of the carboxyl group is replaced by a hydrocarbyl or substituted hydrocarbyl group. Among these is the methyl ester of PGA.sub.2 (J. P. Lee et al., Biochem. J. 105, 1251 (1967)).